Veneer molding process



March 2, 1943, I c; U. GRAMELSPACHER $3 VENEER MOLDING PROCESS Original Filed' Aug. 11, 1939 1 5 Sheets- Shet 1 1 Jn/m in CLARENCEMGRAM4JPACHR IMAM? Q l. g I

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Patented Mar. 2, 1943 Clarence U. Gramelspaoher, Jasper,

Original application August 11, 1939, Serial No. 289,697. Divided and this application July 15, 1940, :Serial No. 345,533 7 2 Claims. (01. 144-399) This invention relates to a process for forming individual sheets of wood veneer or oi. very flexible plywood (say 2 or 3-ply) into articles of desired configuration and more particularly to a process of forming said sheets into articles embg simple or compound curves. The present Yet another object is to carry out a process of the type described above wherein heat is applied to the sheets during the molding process in order to dry and harden the glue or to set the resin invention eliminates the necessity for first making a hat section of Plywood and then bending it into the desired shape by saw-kerflng, corrugating and the like. In a still more particular aspect, the present invention relates to a veneer molding process wherein pressure i exerted on the outside of the sheets to be joined and forming pressure is yieldingly exerted from the inside of the sheets outwardly as by means of an expansible bag, Pressure of any kind can be used for these purposes.

This application is a division of my copending application, Serial No. 289,697, filed August 11, 1939. I

The principal object of the present invention is to devise a method of forming veneer or flexible plywood sheets which are free to slide relative to one another by exerting pressure outwardly from inside of the sheets, while holding the sheets from their exterior in such manner that the inwardly exerted pressure is efiective; the pressure exerted from the outside cooperates with the pressure exerted from the inside to produce an article theconfiguration of which corresponds exactly to that of the outer mold member so that the sure on the sides; however, I have discovered that shape and dimensions of the article are accurately known in advance.

7 Another object is to carry out a process of the foregoing type wherein the inner mold member is in the form of an expansible bag member which is expanded evenly outwardly over the entire ini side area of the sheets to be formed by means.

type above set forth wherein at least one or each pair of adjoining surfaces of the sheets of veneer or thin plywood is precoated with an adhesive which is either liquid at the time of assembly or which becomes liquid under the conditions of 1 molding; this liquid adhesive acts as a lubricant allowing the individual sheets to slide relative to one another, this shifting enabling the quick formation of a more perfect article wherein none of the individual sheets is under stress or tension relative to any other sheet, absolute concentricity throughout the curves being obtained.

where a thermo-setting resin adhesive is employed; this heat may be applied to the sheets from either the outside or the inside; a convenient method is to employ cored outer mold members and to pass a suitable hot fluid under pressure into theexpanslble bag to serve the dual purpose at expanding the same to shape the article and to heat the sheets constituting the article.

Another object is to carry out a process of the foregoing type wherein a base member connects the ends of the veneer or plywood sheets.

Another object is to provide an expansible bag of variable thickness or consistency so that when pressure is exerted against the inside of the clamping form this pressure will be exerted evenly over the entire area; for example, if a spherical bag is used in a rectangular article the pressure on the corners will not be as great as the pres progressively thin out to the portions which contact the corners.

Another object is to devise apparatus for carry ing out the foregoing process.

, Another object is to devise a method and apparatus for molding internally irregularly shaped articles which involves utilization of a rigid mold member contacting on one side the irregular surface, such as an internal insert, and on the other side, which is smooth, the expansible bag.

Other objects will more fully hereinafter appear.

In the accompanying drawings:

Figure 1 is a horizontal section through a mold for a four sided radio cabinet,-as an example, having a baseboard and shows the individual veneer sheets in place with the outer mold members about to beclamped about them and with the expansible rubber bag inner mold member in collapsed form. The showing of a radio cabinet is merely an example of anarticle which can be molded by this process.

Figure 2 is a detail section showing the external clamping and locking means for the end walls.

Fig. 3 is a horizontal section showing the mold in closed position and the bag expanded; the bag is shown as thinned in those areas where expansion is most extensive.

End walls 4 are adapted to be locked intheir 'inward position by means of circular 'heads- 22 Figure 4 is a vertical sectional view showing the I preparation of a five sided article from the flat individual sheets of Figure 6; the openings left at the corners formed by the adjacent side walls will subsequently be filled, in any desirable manner to make a complete five sided enclosure.

Figure is a horizontal section showing a modification in which an insert extends inwardly from the inner face of the article causing sharp internal angles, a rigid auxiliary mold member be- A circular recess 28 is provided at the outermost journaled on theupper ends of shanks 23 which extend downwardly (see Figure 2) through elongated curved slots 24 in base plate I into hinged engagement 24a with a manually operated handle 25 pivoted so as to be swingable vertically about a.

member 261 which is pivoted so as to be swingable horizontally by a pivot member 21 extending pivotally'upwardly into a recess'in base plate I.

end of curved slot 24 to receive circular head 22 when the handle 25' is at its outermost position so that the top of head 22 may be flush with or below the upper surface of base I whereby interference with outward swinging ofend walls 4 is prevented. A catch 29 is provided on the under face of base I into which handle 25 may be inserted to lock the same in clamped position thereby locking mold 4, handle29- is raised vertically out of catch'29' Referring first to Figures 1 to 3 of the drawings,

reference numeral Idesignates a supporting base for the molding device. To base I is attached by means of bolts 5 a vertical rear wallj2 which isstationary and forms a rear mold member.

Hinged to rear wall 2 by means of hinges 3 are end walls 4 which are adapted to-be swung outwardly until parallel with rear-wall 2,"or even further if desired, to allow the lamination assem bly to be inserted in the mold. A front mold wall 6 is slidably mounted on base I by means of a plural'ity of elongated pins I projecting upwardly from and integral with base I (see Figure 4) and which are received within slots 8 in the bottom of,

wall 6. Slots 8 are elongated in the direction in which front wall 6 is slidable.

Front wall 6 is provided on its inward face with an outward recess 43 to receive the baseboard I5 of the exemplary radio cabinet or other object to be molded. Front wall 6 and rear wall 2 are provided with inwardly extending curved corner mold members 9 which may be integral with the walls and which serve to impart the desired Front wall 6, rear wall 2 and end walls 4 are provided with cored passageways I I which are adapted to be supplied with steam or other hot fluid by an inlet pipe III for the purpose of heating the laminations during molding. Any suitable means (not shown) such as a resilient gasket may be provided to seal the passages I I at the point where they interconnect between adjacent mold walls.

A mold cover I2 hinged at I3 to rear wall 2 is adapted to be clamped down over the closed mold preparatory to molding and locked in its clamped position by means of links I4 (see Figure 4) pivoted to the forwarded edge of cover I2 adapted to be locked over hook members I6 fixedly mounted on the front face of front wall 6 by hand locking members I! pivotally carried on the lower end of links It.

walls 4 in their inward position. To unlock walls and is then swung outwardly. and downwardly, thereby allowing walls 4 to move freely outwardly.

' Hinge 240. being at right angles tohandle 25 allows shank 23 to remain-vertical as handle 25 is raised and lowered, butprevents it from sliding out slot 24 due to the pressure of the mold wall. While mechanical means isshown for clamping I end ,walls '4 and front'wall 6 and so designed as to give increasedleverage as the walls close in on the article to be molded, it will be apparent that any external means for exerting clamping pressure inwardly may be employed, such as suitable hydraulic or pneumatic means.

An expansible bag 30 of rubber or the like is provided within the mold cavity and designed when expanded to exert pressure outwardly on the article forcing the laminations outwardly against the externally clamped mold members. Bag 30 has an inlet 3| which extends downwardly through base I, and may be semi-permanently left in the mold by means of nuts 32 on inlet stem 3|. Bag 30 has walls of varying thickness in order that it may expand into substantially the shape of the article. expandingleast for the sides of the article and most-for the curved comers, and more for the ends which-are further apart than for the sides which are closer together. Thus the bag is quite thick at 33 for the closely adjacent sides, is of less thickness at 34 for the face of the article. The same eifect may be obin the bag walls.

tained by varying the stretchability of the rubber Less desirably, the bag may have uniform walls of uniform consistency. The

Frontwall 6 is adapted to be moved inwardly bag may be preformed to approximate when collapsed the ultimate shape ofthe article, being slightly smaller than said ultimate shape.

Bag 30 may be inflated with any suitable fluid such as air under pressure, preferably to a pressure of to 200 pounds per square inch. If it is desired to heat'the article during molding, a hot fluid under pressure such as steam, ora hot liquid such as oil, diphenyLdiphenyl oxide, etc.. is employed as the inflating fluid, either as the sole heating meansor in addition to the employment of a heating medium in the outer mold members.

The veneer sheets indicated-as 40 are pre-coated with a film 4| of adhesive whichwill act as a lubricant allowing the individual sheets to slide relative to one another during the molding. Instead of using veneer sheets, sheets of flexible plywood having an adhesive coating and sumciently pliable to take the initial form may be employed, although the resulting article will not be quite as free of stress. Instead of precoating one side of each lamination, every other lamination may desirably be coated on both faces, thereby simplifying the precoating operation. While the following description refers to using a plu- *rality of veneer sheets 40, it will be understood rality of individual pre-coated veneer sheets 40 a of the same width and of gradually decreasing length are placed in the mold with their middle portions against rear mold wall 2 and their progressively inwardly shorter ends 44 projecting out at the sides of the mold. Ends 44 are then tucked into the mold into the position of Figure 3. End walls 4 are then moved inwardly and clamped at their innermost position by handles 25. "Front wall 6 is then moved inwardly and clamped by means of handle 2|. Lid I2 is then mcveddownwardly and locked with looking members ll. Stem is then admitted to cored passageways I through inlet Ni to heat the mold, which is of metal, to the desired temperature, of say 250 to 300 F., but varying with the type of adhesive employed. Meanwhile bag is inflated through inlet 3! to the desired pressure of 100 to 200 pounds per square inch. The assembly is then allowed to stand until the adhesive has set, which will require from 2 to 20 minutes, but here again the time required will depend on the ad hesive used and the temperature employed. .The

bag is then deflated, the mold cover opened, and

the molded cabinet removed.

In Figure 5, a modification is shown wherein sheets of veneer cut to proper length are used and a baseboard 50 is employed which projects inwardly so as to expose sharp edges 5| which pre-cut to form a bottom or front portion 400 and side portions 40d and end portions We. The intermediate lamination 40b is coated on both sides with adhesive ll and theouter laminations 40a are uncoated. A cutout 40g is provided at each corner intersection of the sides and ends with the front to prevent the formation of an exece'ssively compound curve at this point. The laminations are shaped into the five sided article in the manner illustrated in Figure 4, a curved" member So being provided along each line of bend 40), in order to give the desired curved configuration to the comers and to prevent unduly sharp bending. As before, the outward pressure into the final desired shape.

of an expansiblebag 30 openings left between the edges of the sides 'd and the ends llle may be fllled in any desired manner as, for example, with a suitably shaped piece of wood.

It may readily be seen that the article of in-' vention', as disclosed in Figures 4 and 6, is in the nature of a five sided box having an opentop. The side wallportions 40d and the end wall portions we ofthe precut blanlc sheets of i wood are adapted to be'flexed at the juncture of. the side and end wall portions with the base porj The side wall portions 40d and the tion 40c. end wall portions we, when-arranged to provide a finished product, areiormed at substantially right angles to the base portion 50, whereby the adjacent edges of the side walland end wall portions are adapted to engage and-provide a sealed edge for the box structure. 1

It can readily be seen that theprecut blank, as shown in Figure 6, may be formed in the same type of mold as disclosed in Figures 1 and 3, and by the same method. The side wall portions 40d and the end wall portions'llle may be flexed by any suitable manner at the juncture of the respective portion with the base portion to,

and is then confined within the cavity provided.

by the walls of the mold. The mold is locked together in the manner as heretofore described with regard Figures 1 and 3, whereby the boxlike article being formed will be retained within the mold cavity in rough configuration substantially that which it will assume when a finished product. The expansible bag 30 will then be filled with suitable pressure fluid for causing the It will be understood that I intend to 111- clude as within my invention such modifications as may be necessary to adapt it to varying conditions and uses and as fall' within the spirit of the appended claims. For example, I may employa thin flexible electrical heating element around the expansible bag to transmit the pressure of the bag to the article being formed while transfer the pressure from the bag to the article 7 or I may use a layer of cloth, asbestos, metal foil or the like in place of a layer of wood or in ad a dition to the layers of wood. Similarly, while J the above disclosure refers to liquid adhesive,

I may use any adhesive in sheet form, such as "Tego" glue film which, is a dry film on a very thin tissue base and which is placed between layers of veneer rather than coated thereupon. This film comprises a phenol-formaldehyderesin' sheets I may also use other resins on the marshapes the laminations Subsequently, the v ket which are allowed to dry after being spread on the veneer in liquid form and mustbe' thoroughly dry before pressing, these resins usually requiring solvents other than water, such as alcohol or the like. In this way, -I may avoid the use of aqueous liquid adhesives, the watervof which may tend to swell or distort the sheets of veneer. Whereas I have illustrated the use of three and four laminations, I am not limited to three or four'ply articleabut may employ any number of plies, depending upon the thickness, strength or shape required.

Having thus fully described my invention,

what I claim as new and-desire to secure by Letters Patent is:

1. A method of forming an article from individual-sheets of wood, wherein the article has an irregular surface having sharp inward edges comprising disposing the sheets with adhesive between adjoining surfaces within a mold of ap-'- proximately the desired form, inserting a baseboard having irregularly shaped side edges, so shaped as to conform to the said irregular surfaceof said sheets and inserting on the inside of the assembled sheets and baseboard a member having a smooth inner face and an opposite outer face shaped to correspond with the irregu lar face of the article, inserting an expansible member inwardly of said article, admitting a fluid under pressure to said expansible member to thereby expand the same against said first named member and the inside surfaces of said sheets and to exert forming pressure outwardly upon said sheets, and maintaining the fluid pressure until the adhesive between said sheets sets. 2. An apparatus for forming a laminated article from sheets of wood, said article includextending therefrom and having an irregular in- 1 ner surface having sharp edges produced by a baseboard having irregularly shaped side edges in abutting relation with the side edges of the sheets and the surface thereof extending beyond the inner surface of the sheets comprising, a mold having a plurality of movable walls to form a cavity shaped to the exterior configuration of the article being formed, said walls being movable to open said mold to permit insertion of the plurality of sheets of wood therein in adjacent relationship with adhesive therebetween and to permit the insertion of said baseboard, a flller member adapted to be disposed upon said baseboard having one smooth face and the opposite face thereof shaped to conform with the irregular surface formed by the baseboard, the walls of said mold being adapted to be closed upon the sheets to confine the same therein together with said baseboard and said flller member and cause the sheets to assume a configuration within the mold roughly that of the cavity, an expansible member positioned within said mold and within the confines of the roughly shaped article adapted to engage the inner surface of the article to be formed from said sheets and said filler member, and means for admitting fluid under pressure within said expansible member to expand the same outwardly against the sheets and said filler member to cause same to move into. the proper position relative to each other and assume the configuration of the cavity and maintaining the pressure until the adhesive sets.

CLARENCE U. GRAMELSPACHER. 

